Given the controversy of the late 1960s and early 1970s over the possible induction of chromosomal damage by psycho-active agents like LSD and marihuana, the peyote study of Teplitz et al (p 299), is reassuring. It is, first of all, comforting to know that in vivo studies of agents that are possible chromosomal mutagens can produce, when properly designed and executed, clear-cut results....